In the pharmaceutical industry, it is necessary to test the reaction (including biological activity) of chemical A to chemicals B1–Bn, where n can be a large number, on the order of millions.
A popular method is that of providing an array of substances B1–Bn on a plastic card and placing substance A in contact with each of the Bn. Commercially available plastic card arrays include 96 and 384 wells. The well diameters are of the order of few millimeters. The method of chemical placement or dispensing usually is by pipettes. There are computer assisted scanners used to type the chemical interactions.
Since there are millions of combinations of chemicals to test to exhaust the possibilities, it takes years for companies that are involved in drug discovery, to bring a successful drug to the market. With the current speed of computer assisted scanning devices, it is possible to reduce the drug discovery time, for example, by increasing the number of samples scanned at a time. This is possible if we can pack more number of wells, for example, in a given volume. A larger number of wells in a given volume also reduces the amount of costly chemicals to be used in a given well.
The plastic cards are usually formed by extrusion and the precision of the hole diameter and location within the array is not adequate enough to fabricate micro holes and channels. This essentially limits the extendability of plastic in this field.
The pharmaceutical industry is searching energetically for micro devices, with multiple thousands of wells with diameters of the order of 100 microns and channels connecting the selective wells at different levels within the array.